Mixing syringe

ABSTRACT

A movable mixing disc is inserted into a regular syringe. The mixing disc has a small hole covered by a fine screen, allowing only saline solution to get behind the disc. When the plunger of the syringe is pressed, the saline solution emerges from the mixing disc hole as a high velocity jet, stirring up the settled particles. As the ejection continues, the mixing disc is pushed forward by the plunger in order to eliminate any unused volume.

FIELD OF THE INVENTION

The invention is in the medical field, and is particularly useful in percutaneous procedures such as embolization.

BACKGROUND OF THE INVENTION

In certain medical procedures, such as blood vessel embolization, it is desired to inject particles into the body. The procedure is a minimally invasive alternative to surgery. The purpose of embolization is to prevent blood flow to an area of the body, which effectively can shrink a fibroid, such as a uterine fibroid. It can also shrink a tumour or block an aneurysm. It is typically done by injecting blocking particles into a blood vessel.

The procedure is carried out as an endovascular procedure by a radiologist in an interventional suite. It is common for most patients to have the treatment carried out with little or no sedation, although this depends largely on the organ to be embolized.

Access to the organ in question is acquired by means of a guidewire and catheter. The position of the correct artery or vein supplying the undesired tissue in question is located by X-Ray images. These images are then used as a map for the radiologist to gain access to the correct vessel by selecting an appropriate catheter and or wire, depending on the shape of the surrounding anatomy

The blocking particles are mixed into a saline solution, sometimes a contrast agent is added (to make the solution opaque to X-Rays). The blocking particles have to be of certain sizes, typically between 0.1 mm to 1 mm, in order to block the blood vessel at the right diameter. Such particles tend to settle very quickly out of the solution as they are heavier than water, causing an uneven concentration of particles during the injection. The settling occurs in as little as a few seconds. It is inconvenient to keep shaking the syringe used for injection, as the whole process is performed in a few seconds and the doctor has to concentrate on injecting the correct amount. It is desired to have a syringe that can keep the particles uniformly dispersed in the saline solution regardless of delays in the injection process or speed of the injection. Since the syringes used are low cost disposable items, it is desired that the device used to keep the particles uniformly dispersed will also be very low cost and disposable. The ideal mixing syringe needs the following attributes:

A. Ability to be re-filled multiple times during a procedure. This rules out any single-use designs, typically using the rupturing of a membrane to allow mixing. B. Generate a strong mixing action, preferable by creating a vortex in the mixture. C. Use the minimum modification to a standard syringe.

Prior art mixing syringes, such as disclosed in U.S. Pat. No. 7883490 are designed to mix together two materials stored separately in two compartments. They are not designed to stir up a pre-mixed solution. Prior art syringes designed to stir-up embolization mixtures, such as disclosed in US2009/0247985, are needlessly complex. Also, many of the prior art mixing syringes are not designed to be filled with the pre-mixed solution just before use. This is required during embolization, as the correct volume and ratio of saline, particles and contrast agent has to be customized to the procedure by the doctor. The current invention acts as a regular syringe, allowing filling and injecting at any time, but it keeps the solution stirred up during injection. Similar to a regular syringe, it can be re-used several times during a procedure, if more particles have to be injected. The invention can be manufactured out of a regular syringe, which is a very low cost item.

SUMMARY OF THE INVENTION

A movable mixing disc is inserted into a regular syringe. The mixing disc has a small hole covered by a fine screen, allowing only saline solution to get behind disc. When the plunger of the syringe is pressed, the saline solution emerges from the mixing disc hole as a high velocity jet, stirring up the settled particles. As the ejection continues, the mixing disc is pushed forward by the plunger in order to eliminate any unused volume.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general view of the invention.

FIG. 2 shows a cross-section of the mixing disc as well as a front view. .

FIG. 3 shows the action of the mixing disc.

FIG. 4 is a cross section and a front view of a mixing disc stamped out of sheet metal.

FIG. 5 shows a version of the invention not requiring modifications to the syringe.

DETAILED DESCRIPTION

Referring now to FIG. 1, the mixing syringe is a regular syringe with the addition of a mixing disc. A syringe 1 includes a plunger 2 and a seal 3 in order to eject the liquid 6 via tube 4. A piston-like mixing disc 5 is added into the syringe. The initial position of disc 5 is shown as 5′, with plunger seal 3 touching disc 5. As liquid and particles are sucked into syringe 1, seal 3 moves farther from disc 5 to create a vacuum. Disc 5 moves as well, until stopped by slight ridge 8. The size of the ridge is exaggerated in FIG. 1 for clarity. It only needs to reduce the inside diameter by about 0.2-0.3 mm.

Flexible seal 3 easily passes over such a ridge. The particles 7 are sucked into the syringe via tube 4 and quickly settle as shown in FIG. 1. The particles do not accumulate in the section between plunger seal 3 and disc 5 as disc 5 includes a filter with pore sizes smaller than the particles. This is shown in FIG. 2. Disc 5 has one or more holes 9 covered by filter mesh 10. It is desired to chamfer hole 9 under screen 10 to increase the effective area of the screen. The screen can also be mounted as a flexible flap, being pushed out of the way during ejection of the fluid. The conical shape of disc 5 is matched to the shape of the conical seal 3 and the conical tip of the syringe. This eliminates trapped fluid between the seal 3 and the syringe outlet at the end of the stroke. The conical shape of disc 5 also aids the removal of any trapped air bubbles, as they float to the top of disc 5 and escape when syringe is held vertically. As plunger 3 is moved towards disc 5 the liquid 6 is ejected via hole 9 at a high velocity, mixing up particles 7 and liquid 6. This is shown in FIG. 3.

From the moment seal 3 touches disc 8 the disc is pushed forward towards the tube 4 until the syringe is empty and disc 5 is in position 5′. The operation can now be repeated, if desired.

It is desirable to make hole 9 at an angle to the axis of the syringe in order to create a vortex. An even more effective vortex can be created if hole 9 is molded as a curved arc, both in the plane of the drawing and also in the plane perpendicular to the drawing.

Disc 5 can be molded in one piece, including screen 10. Alternatively, screen 10 can be bonded to molded disc 5. The fit between disc 5 and bore of syringe 1 is not critical as the particles are relatively large. It was found out that for best results the diameter of disc 5 should be 0.1-0.2 mm smaller than the inside diameter of syringe 1.

While the example given is for embolization, the invention can be used to mix and two components, including two liquids.

Disc 5 can also be made out of pressed sheet metal 11. This is shown in FIG. 4. In this case hole 9 and screen 10 are replaced by miniature stamped louvres 12 (similar to a miniature venetian blind) acting both as a screen and as a flow director. Recommended material is type 316L stainless steel or aluminum, with thickness between 0.1 to 0.3 mm. The thin wall allows seal 3 to enter into the hollow disc and squeeze out all the liquid.

In order to eliminate the need of molding custom syringes it was found out that the slight ridge 8 can be formed in existing syringes by briefly heating up the area of ridge 8 and pressing the walls in slightly, using a split ring slightly smaller than the outside diameter of the syringe. Other ways of creating a ridge without molding is pressing into the syringe a thin walled ring, held by friction.

If desired the invention can be manufactured out of a standard disposable syringe, without any modifications. The movable disc 5 is attached to the outlet side of the syringe with a short string that only allows it to move a limited distance. The string 13 is bonded by heat to the syringe or uses an anchor 14. This is shown in FIG. 5.

In operation tube 4 is first inserted into a mixing bowl where the ingredients are mixed together. The mixture is sucked into the syringe. After filling the syringe is held vertically to help trapped air escape and plunger moved to expel all air. Afterwards tube 4 is moved to the catheter or needle used for the procedure and mixture is injected.

An additional improvement in mixing is to adjust the density of particles 7 to match the density of liquid 6, typically a saline solution with a density around 1. since the materials used to make particles 7 (plastic, glass or ceramic) have a density greater than 1, they have to be made hollow. The technology of manufacturing small hollow spheres, known as micro-balloons, is well known and many polymers as well as glasses are commercially available in micro-balloon form. One supplier is Henkel , (http://www.henkelna.com/cps/rde/xchg/henkel_us/hs.xsl/brands-1556.htm?iname=Dualite %25C2%25AE&countryCode=us&BU=industrial&parentredDotUID=0000000GFR&redDotUID=000 0000GFR&brand=000000QTQE

Both ideas can be combined: micro-balloon shaped polymer or glass spheres with a density around 1 can be dispensed from a syringe with a mixing disc. 

1. A syringe configured to contain a mixture of a liquid and solid particles, the syringe comprising a mixing disc configured to generate a liquid jet for mixing the liquid and the solid particles during ejection of the mixture, the mixing disc comprising a screen having pore sizes smaller than the solid particles.
 2. A syringe comprising: a cylindrical body; a plunger; an outlet; and a movable disc located between the plunger and the outlet of said the syringe, the movable disc comprising a hole configured to create a jet of liquid when the syringe is contains a liquid and the plunger is moved to eject the liquid, wherein the movable disc comprises a screen having pore sizes smaller than particles configured to be mixed with the liquid.
 3. A method of displacing a mixture of a liquid and solid particles by using a syringe, the method comprising: disposing with a mixture of liquid and solid particles within the syringe; separating a portion of the liquid from the mixture by sucking it through a screen having pore sizes smaller than the particles, the screen coupled to a movable disc inside the syringe; and ejecting the separated liquid into the mixture to create a flow pattern in the mixture, the flow pattern configured to prevent the solid particles from settling.
 4. A syringe as in claim 1, further comprising a syringe body and a plunger, wherein the mixing disc is free to move inside syringe body along a portion of the movement range of the plunger.
 5. A syringe as in claim 1, further comprising a syringe body and a plunger, wherein the mixing disc is free to move inside syringe over a limited range, the range being limited by a ridge inside the syringe body.
 6. A syringe as in claim 1, wherein the mixing disc comprises molded plastic.
 7. A syringe as in claim 1, wherein the mixing disc comprises pressed thin metal.
 8. A syringe as in claim 1, wherein the jet is created by a slanted hole in the mixing disc.
 9. A syringe as in claim 1, wherein the syringe is manufactured by bonding a string to an unmodified disposable syringe.
 10. A syringe as in claim 1, wherein the solid particles comprise hollow particles having a density substantially matched to the density of the liquid.
 11. A method as in claim 3, wherein motion of the movable disc is restricted by a ridge inside the syringe.
 12. A syringe method as in claim 2, wherein motion of the movable disc is restricted by a ridge inside the syringe.
 13. A syringe method as in claim 1, wherein the shape of the mixing disc minimizes the volume of trapped liquid in the syringe.
 14. A syringe method as in claim 2, wherein the shape of the movable disc minimizes the volume of trapped liquid in the syringe.
 15. A syringe as in claim 2, wherein the syringe is manufactured by bonding a string to from an unmodified disposable syringe.
 16. A method as in claim 3, wherein the syringe is manufactured by bonding a string to an unmodified disposable syringe.
 17. A syringe configured to contain a mixture of a liquid and solid particles, the syringe comprising a mixing disc configured to generate a liquid jet for mixing the liquid and the solid particles during ejection of the mixture, the mixing disc comprising a louvered hole with openings smaller than the solid particles.
 18. A method of displacing a mixture of a liquid and solid particles using a syringe, the method comprising: disposing a mixture of liquid and solid particles within the syringe; separating a portion of the liquid from the mixture by sucking it through a louvered hole with openings smaller than the particles, the louvered hole coupled to a movable disc inside the syringe; and ejecting the separated liquid into the mixture to create a flow pattern in the mixture, the flow pattern configured to prevent the solid particles from settling. 